884
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Figure 1.General view of shaking table model
2. 2.
Materials
The tire chips used in this study was made from
discarded tires. The particles shape was very irregular
and angular. The tire chips particles have negligible
water absorption, and very small volumetric
compression due to isotropic pressure. Table 1
demonstrates physical properties of tire chips.
Table 1. Physical properties of tire chips material
Material
D
10
(mm)
D
50
(mm)
C
c
C
u
G
s
Tire
chips
2.1
3.9
0.99
2.05
1.16
Firoozkuh No.161 sand was used for the mixture in
reinforced side, and pure sand in unreinforced side.
Table 2 demonstrates physical properties of sand.
Table 2.physical properties of sand material
Material
G
s
e
max
e
min
Cc
Cu
D50
(mm)
Sand
1.16
0.874
0.548
0.97
2.58
0.3
2.3.
Experimental procedure
Uchimura et al. (2007) presented following relation to
calculate mixture ratio of tire chips that were evaluated
by the dry weight of the tire chips relative to the total
mixture material:
TC
r
S TC
M TC
M M
(1)
(
: Tire chips content,
r
TC
TC
M
: Weight of tire chips ,
S
M
: Weight of Firoozkuh sand).
In this study 4 mixture ratio (TC
r
=10%, TC
r
=20%,
TC
r
=30% and TC
r
=40%) were selected. Maximum
mixture ratio was limited to 40 percent, because if tire
chips content were higher, the sand could not fill the
entire voids among tire chips particles and the model
became non-uniform.
Relative density of tire chips-sand mixture was
calculated by following relation:
max
max min
(
(
)
s
r
e
e
D
e
e
)
(2)
(
s
e
min
e
: sand void ratio,
: maximum void ratio of sand
,
: minimum void ratio of sand).
max
e
Where
s
e
can be calculated as:
Total
s
Tc
s
s
V V V
e
V
(3)
(
: Total volume of mixture,
Total
V
s
V
: Volume of sand
particles ,
:Volume of Tire chips particles)
Tc
V
Both of unreinforced (pure sand) and reinforced (tire
chips-sand mixture) models were prepared by wet
tamping method, in which soil is mixed with 5% water.
Each model (reinforced or unreinforced) was
prepared in six layers. The required weight for each
layer was considered based on the desired density
(equivalent value of the maximum void ratio or zero
relative density) and exact volume of the layer. Each
portion was placed into the model container and then
tamped with light trowel to reach desired level. Carbon
dioxide (CO2) was allowed to pass through the
specimen at a low pressure in order to replace the air
that trapped in the pores of the specimen. Then water
was allowed to flow upward through the bottom of the
container at low pressures in order to flush out the CO2
that cause increasing the final degree of saturation.
Vibration with approximate uniform amplitude and 2.1
Hz freq was manually applied to the container (the
shaking table was designed to vibrate at around 2 Hz
frequencies).
3
TEST RESULTS AND DISCUSSION
3.1.
Time history of acceleration
Figure 2 is a typical plot of time history of base
acceleration measured by accelerometers (a5). It is
noticeable that in all models base acceleration was
continued for 23 second. Results indicated that
acceleration within the soil tends to be increased towards
the soil surface. On the other hand, after initial
liquefaction (that occurred at un-reinforced models and
also reinforced model with TC
r
=10%), acceleration is
decreased due to the increase in excess pore water
Pressure.
(d)
Figure 2.Typical Time History of Base Acceleration
3.2.
Shear stress-strain relationship
From the original shear beam equation, shear stress τ at
any depth z may be written as the integration of density
(ρ) times acceleration (ü) through higher levels (Eq.4).
0
z
udz
(4)
A linear fit is recommended between adjacent pairs of
instruments, which may be extrapolated from the top
pair to surface (Eq. (5)).
